Which two layers constitute the periosteum?

Which two layers constitute the periosteum?

• A. Fibrous outer layer and osteogenic inner layer
• B. Endosteum and perichondrium
• C. Cartilage and bone
• D. Muscle and tendon

Answer: (A)

The periosteum has two distinct layers: an outer fibrous layer and an inner osteogenic (cambial) layer. The outer layer is dense irregular connective tissue rich in collagen, providing protection and anchoring the membrane to surrounding structures via Sharpey’s fibers. The inner layer contains osteoprogenitor cells that can differentiate into osteoblasts, giving the periosteum its bone-forming and repair capability. This combination explains how the periosteum supports growth in thickness and fracture healing, and it distinguishes it from other membranes like the endosteum (inner bone lining) or perichondrium (around cartilage).

The periosteum has two distinct layers: an outer fibrous layer and an inner osteogenic (cambial) layer. The outer layer is dense irregular connective tissue rich in collagen, providing protection and anchoring the membrane to surrounding structures via Sharpey’s fibers. The inner layer contains osteoprogenitor cells that can differentiate into osteoblasts, giving the periosteum its bone-forming and repair capability. This combination explains how the periosteum supports growth in thickness and fracture healing, and it distinguishes it from other membranes like the endosteum (inner bone lining) or perichondrium (around cartilage).